Electrode mounting



Feb 11, 1936. w. w. EITEL ET AL.

ELECTRODE MOUNTING Filed Aug. 15, 1955 INVENTORSW WILL/AM n E/TEL.

JACK Mc CULLOUGH.

' ATTORNEY Patented Feb. 11, 1936 ELECTRODE MOUNTING William W. Eiteland Jack McCullough, San

Bruno, Calif., assignors to Heintz & Kaufman, Ltd., San Francisco,Calif., a corporation of Nevada Application August 15, 1933, Serial No.685,204

3 Claims.

Our invention relates to means for and method of mounting an electrode,and more particularly to mounting electrodes in a thermionic tube.

Among the objects of our invention are: To provide a means and method ofmounting electrodes in a thermionic tube whereby strength and rigidityof structure is obtained; to provide a three point support forelectrodes mounted within a thermionic tube; to provide long leakagepaths between electrodes in a thermionic tube; to provide a means forand method of mounting electrodes in a thermionic tube of cylindricalshape without materially changing the contour of the envelope; and toprovide a thermionic tube of minimum size having long leakage pathsbetween electrode supports.

Other objects of our invention will be apparent or will be specificallypointed out in the description forming a part of this specification, butwe do not limit ourselves to the embodiment of our invention hereindescribed, as various forms may be adopted within the scope of theclaims.

Before the advent of extended use of the higher radio frequencies inradio communication, it was customary to mount all the electrodes of amultielectrode thermionic tube capable of self-oscillation oramplification, on .a single envelope extension or stem, usuallyreentrant, the supporting leads being sealed through a single pinch orfused portion of the stem. Of necessity these leads were close togetherand practically parallel while passing through the seal.

When, however, such devices were used for high frequency oscillationgeneration or amplification, electrolysis of envelope material andconsequent shorting occurred at the pinch, necessitating completeseparation of the anode, cathode and control electrode leads. Thisseparation in turn has led to the mounting of such electrodes from thesides, top and bottom of the tube envelope in projecting arms, thusgreatly enlarging the over-all space required to house the tube.

It is also important in modern tubes that the electrodes be firmlysecured to the envelope and that they be so mounted as to preventrelative motion under the influence of heat, electrical fields ormechanical vibration. The present custom of mounting in side or endenvelope arms places the electrode, which is usually quite heavyespecially in the power tubes, at the end of a long support, and slightdistortions of the envelope material cause large displacements of theelectrode. As the electrode mounting points are widely spaced, motion ofthe electrodes relative to one another is difiicult to prevent.Insulators locking the electrodes against such movement are difficult,if not, impossible, to install in this type of tube, as the spacedmounting points necessitate individual insertion and sealing of thevarious electrodes.

Our invention attains, in broad terms, wide spacing of the electrodemounting points with minimum length of support within an envelope, byproviding the electrodes, which are preferably cylindrical, with supportmembers, preferably three peripherally attached wires. The ends of thesewires are beaded with a material which will seal readily to the envelopematerial. If the envelope be of a certain type of glass, for example,the beads may be of the same type, or one so closely allied as to sealto the envelope without developing strain at the point of fusing. It isalso desirable that the bead make good contact and stick tightly to theend of the support wire. If an envelope of the usual shape is used,having a hemispherical end and cylindrical side walls, the beads may besealed either to the end portion, or by bending the support membersoutwardly, to the side walls. It is often desirable to seal oneelectrode to the end portion and one or more others to the side walls,leaving the remaining end for sup-porting other electrodes which do notrequire such wide spacing of leads or mounting supports, such as acathode for example.

The broad aspects of our invention may be more fully appreciated byreference to the drawing in which:

Figure l is a view in elevation of a step in the mounting of anelectrode within an envelope in accordance with our invention.

Figure 2 is a View partly in section and partly in elevation of themounted electrode.

Figure 3 is a sectional View taken as indicated by the line 3-3 inFigure 2.

Figure 4 is a longitudinal view partly in section and partly inelevation of an envelope having two electrodes mounted therein.

In the preferred embodiment illustrated, an envelope l, preferablyhaving a hemispherical end 2 and a cylindrical side wall 4, is providedwith a tubulation 5. We have shown this tubulation as being in thecenter of the hemispherical portion, although it may be in otherlocations, or omitted as will be later explained. The envelopeillustrated is of the size and shape hitherto used in the popular 50watt three-electrode oscillator and amplifying tube, in which allelectrodes have formerly been mounted on a reentrant stem sealed in theend opposite the hemispherical portion, and is customarily blown fromborosilicate glass, known in the art under the trade-name "Pyrex, or aclosely allied glass sold under the trade designation of G702P.

An electrode, in this example a cylindrical anode 6, provided with finsl to increase heat dissipation, has welded thereto anode support members9 preferably peripherally arranged, equally spaced and three in number.These support members extend beyond the anode, and are preferably madefrom tungsten wire. As either of the above mentioned glasses sealreadily to tungsten, the ends of the support members may be covered withsmall portions of such glass to form support beads I 0 which adherefirmly to the wires. As is well known in the art, G702P seals totungsten better than Pyrex and as the latter glass is somewhat harderthan the former, it is customary to make the portion of the envelopethrough which tungsten leads are sealed of G702P, the remainder of theenvelope being Pyrex. Following that teaching we prefer therefore tobead the wires with G702P and make the main body of the envelope ofPyrex, the two glasses, however, being so closely allied that they willfuse without strain.

If it is desired that a lead separate from the support members heprovided for the electrode,

an anode lead I l is provided with a lead bead E2,

and is connected to the anode by a flexible link M.

A step in the mounting of the electrode is shown in Figure 1. Here boththe envelope and the beaded anode are chucked in a glass working latheand rotated, a narrow fire I5 being used to heat the support beads l8and a broader fire l6 employed to heat the hemispherical end portion.When the heated portions reach fusing temperature, the anode is movedinside the envelope until the beads touch the hemispherical portion andfuse thereto. The rotation is continued and the end annealed by gradualreduction of the temperature of the broad flame. The heat is thenwithdrawn and the anode mounting is complete. During the fusing theanode lead has entered the tubulation and the anode lead bead sealed tothe envelope. The completed mount is shown in Figure 2.

The mount thus formed is exceptionally sturdy. It gives a shortthree-point support for the anode, and as the mounting operation may beperformed on a lathe the spacing relations between the envelope and theanode can be made absolute and uniform in quantity production. There isno disturbance of the exterior surface of the envelope, its contourremaining unchanged. It is, however, possible to omit the special anodelead, tubulate off center and run one or more of the anode supportmembers through the glass to obtain the electrical connections. Weprefer, however, to utilize the separate lead.

The same general method may also be used to support electrodes from thecylindrical side wall 4. Figure 4 shows an example in which the anodehas been mounted as above described, and in which an additionalelectrode, a grid I! was provided with grid support members I8 whichwere outwardly bent, and the ends beaded. In this case the grid andenvelope were chucked and rotated with the grid in the final position,the support beads being located closely adjacent the side wall. Fireswere then applied to the outside of the envelope opposite the beads. Theforce of the fires, after the envelope heats, causes the side wall tocontract sufficiently to melt down on the beads, fuse thereto, a slightinternal air pressure being sufficient to restore the side wall to itsoriginal shape, slightly elongating the bead seal. The envelope is thenannealed and removed from the lathe.

We then have a concentrically mounted grid and anode, each supported atthree points from the inner surface of the envelope. As they both wereaccurately positioned when mounted they are in definite spacedrelationship and remain so during operation of the tube, the shortnessof the support members and the three-point support resisting all warpingtendencies.

The remaining end of the tube may be used to mount a cathode on a sternin the usual manner, a grid lead 19 passing through the envelope at anyconvenient point apart from the cathode leads, preferably through thestem seal.

It will be apparent also that additional concentric electrodes may bemounted inside of the grid I? in exactly the same manner as the grid wasmounted, the leads from these other electrodes each made a little longerthan the one before to place the bead seals of each on a lower level, orthe bead seals may be staggered on the same level without lengtheningthe supports.

Apart from the sturdiness and absolute alignment, other advantages areapparent. The size of the original envelope is not enlarged and no sidearms are used to increase the space needed to mount the tube. The anodesupports are widely separated from those of the other electrodes and '75to or more watt structures may be placed in the envelope of the usual 50watt size and then used for high frequency work. High power tubes madeas described are ideal for air- 3' craft transmitters where space is ata premium, and the rigid construction eliminates all trouble fromvibration.

We claim:

1. In combination, an envelope having a hemispherical end andcylindrical side walls, an anode having spaced circumferentiallyattached leads extended from one end of said anode only, said leadsbeing separately sealed to said hemispherical end, and a cylindricalgrid concentrically poof said envelope above the level of said anode,and

a second tubular electrode positioned within said anode by electrodesupports extending only from the end of said tubular electrode oppositeto the support attachments of said anode and terrninat ing in theenvelope side walls below the level of z said anode whereby therespective envelope terminations of said supports are separated by adistance at least equal to the length of said anode.

3. In combination, an envelope, a pair of concentric tubular electrodestherein, one of said electrodes being supported solely by a plurality ofsupport wires extending from one end thereof and separately sealed tosaid envelope, and the other electrode being supported solely by supportmeans extending from the other end thereof and terminating on the sidewalls of said envelope, the respective support terminations beingseparated by at least the length of said electrodes.

WILLIAM W. EITEL. JACK MCCULLOUGH.

